Superfluidlike motion of an absorbing body in a collisional plasma

Motion of a small charged absorbing body (micrograin) immersed in a stationary weakly ionized high pressure plasma environment is considered. It is shown that the total frictional (drag) force acting on the grain can be directed along its motion, causing the grain acceleration. At some velocity, the forces associated with different plasma components can balance each other, allowing free undamped superfluid motion of the grain. The conditions when such behavior can be realized and the possibility of a superconductive grain current are discussed in the context of complex (dusty) plasmas.

Characterization of the mitochondrial inner membrane protein translocator Tim17 from Trypanosoma brucei

Mitochondrial protein translocation machinery in the kinetoplastid parasites, like Trypanosoma brucei, has been characterized poorly. In T. brucei genome database, one homolog for a protein translocator of mitochondrial inner membrane (Tim) has been found, which is closely related to Tim17 from other species. The T. brucei Tim17 (TbTim17) has a molecular mass 16.2kDa and it possesses four characteristic transmembrane domains. The protein is localized in the mitochondrial inner membrane. The level of TbTim17 protein is 6-7-fold higher in the procyclic form that has a fully active mitochondrion, than in the mammalian bloodstream form of T. brucei, where many of the mitochondrial activities are suppressed. Knockdown of TbTim17 expression by RNAi caused a cessation of cell growth in the procyclic form and reduced growth rate in the bloodstream form. Depletion of TbTim17 decreased mitochondrial membrane potential more in the procyclic than bloodstream form. However, TbTim17 knockdown reduced the expression level of several nuclear encoded mitochondrial proteins in both the forms. Furthermore, import of presequence containing nuclear encoded mitochondrial proteins was significantly reduced in TbTim17 depleted mitochondria of the procyclic as well as the bloodstream form, confirming that TbTim17 is critical for mitochondrial protein import in both developmental forms. Together, these show that TbTim17 is the translocator of nuclear encoded mitochondrial proteins and its expression is regulated according to mitochondrial activities in T. brucei.

Protein phosphatase 5 is required for Hsp90 function during proteotoxic stresses in Trypanosoma brucei

Trypanosoma brucei, a parasitic protozoan that causes African trypanosomiasis in human and domestic animals, adapt in various environments during their digenetic life cycle. In this study, we found that Hsp90 is crucial for the survival of this parasite. Inhibition of Hsp90 activity by geldanamycin (GA) reduced cell growth and increased the level of Hsp90. Both the bloodstream and procyclic forms of T. brucei showed a several-fold greater sensitivity than the mammalian cells to GA and also to 17-AAG, a less toxic derivative of GA, suggesting that Hsp90 could be a potential chemotherapeuric target for African trypanosomiasis. T. brucei Hsp90 interacts with the protein phosphatase 5 (PP5) in vivo. Under normal growth conditions, T. brucei PP5 (TbPP5) and Hsp90 are primarily localized in the cytosol. However, with increase in growth temperature and GA treatment, these proteins translocate to the nucleus. Overproduction of TbPP5 by genetic manipulation reduced the growth inhibitory effect of GA, while knockdown of TbPP5 reduced cell growth more in the presence of GA, as compared to parental control. Depletion of TbPP5, however, did not prevent the induction of Hsp90 protein level during GA treatment. Together, these results suggest that TbPP5 positively regulates the function of Hsp90 to maintain cellular homeostasis during proteotoxic stresses in T. brucei.

Trypanosoma brucei: differential requirement of membrane potential for import of proteins into mitochondria in two developmental stages

Trypanosome alternative oxidase (TAO) and the cytochrome oxidase (COX) are two developmentally regulated terminal oxidases of the mitochondrial electron transport chain in Trypanosoma brucei. Here, we have compared the import of TAO and cytochrome oxidase subunit IV (COIV), two stage-specific nuclear encoded mitochondrial proteins, into the bloodstream and procyclic form mitochondria of T. brucei to understand the import processes in two different developmental stages. Under in vitro conditions TAO and COIV were imported and processed into isolated mitochondria from both the bloodstream and procyclic forms. With mitochondria isolated from the procyclic form, the import of TAO and COIV was dependent on the mitochondrial inner membrane potential (delta psi) and required protein(s) on the outer membrane. Import of these proteins also depended on the presence of both internal and external ATP. However, import of TAO and COIV into isolated mitochondria from the bloodstream form was not inhibited after the mitochondrial delta psi was dissipated by valinomycin, CCCP, or valinomycin and oligomycin in combination. In contrast, import of these proteins into bloodstream mitochondria was abolished after the hydrolysis of ATP by apyrase or removal of the ATP and ATP-generating system, suggesting that import is dependent on the presence of external ATP. Together, these data suggest that nuclear encoded proteins such as TAO and COIV are imported in the mitochondria of the bloodstream and the procyclic forms via different mechanism. Differential import conditions of nuclear encoded mitochondrial proteins of T. brucei possibly help it to adapt to different life forms.

Functional characterization of the serine/threonine protein phosphatase 5 from Trypanosoma brucei

PP5 is a member of the PPP family of serine/threonine protein phosphatases and is present in all eukaryotes. We previously cloned and characterized a PP5 homologue from Trypanosoma brucei. Here, we synchronized the T. brucei procyclic form by hydroxyurea treatment and showed that TbPP5 expression is regulated during cell cycle progression. TbPP5 transcript and protein levels were maximal in the G1 phase of the cell cycle, and reduced about 3-fold in the G2/M phase. To further evaluate its function, TbPP5 expression was depleted in both procyclic and bloodstream forms of T. brucei by RNA interference. In the procyclic form, TbPP5 knockdown resulted in a moderate reduction in cell growth. However, in the bloodstream form, ablation of TbPP5 caused an 8-fold decrease in cell growth. Furthermore, TbPP5 overexpression conferred the ability of procyclic cells to grow in serum-deprived conditions suggesting that TbPP5 acts downstream of serum factor-induced growth in T. brucei. Taken together; these findings suggest that a serum factor (or factors) induces up-regulation of TbPP5 expression during the G1 phase, which is required for proper cell growth.

Novel inhibitors of the trypanosome alternative oxidase inhibit Trypanosoma brucei brucei growth and respiration

African trypanosomiasis is a deadly disease for which few chemotherapeutic options are available. The causative agents, Trypanosoma brucei rhodesiense and T. b. gambiense, utilize a non-cytochrome, alternative oxidase (AOX) for their cellular respiration. The absence of this enzyme in mammalian cells makes it a logical target for therapeutic agents. We designed three novel compounds, ACB41, ACD15, and ACD16, and investigated their effects on trypanosome alternative oxidase (TAO) enzymatic activity, parasite respiration, and parasite growth in vitro. All three compounds contain a 2-hydroxybenzoic acid moiety, analogous to that present in SHAM, and a prenyl side chain similar to that found in ubiquinol. ACD15 and ACD16 are further differentiated by the presence of a solubility-enhancing carbohydrate moiety. Kinetic studies with purified TAO show that all three compounds competitively inhibit TAO, and two compounds, ACB41 and ACD15, have inhibition constants five- and three-fold more potent than SHAM, respectively. All three compounds inhibited the respiration and growth of continuously cultured T. b. brucei bloodstream cells in a dose-dependent manner. None of the compounds interfered with respiration of rat liver mitochondria, nor did they inhibit the growth of a continuously cultured mammalian cell line. Collectively, the results suggest we have identified a new class of compounds that are inhibitors of TAO, have trypanocidal properties in vitro, and warrant further investigation in vivo.

Trypanosome alternative oxidase: from molecule to function

Trypanosome alternative oxidase (TAO) is the cytochrome-independent terminal oxidase of the mitochondrial electron transport chain. TAO is a diiron protein that transfers electrons from ubiquinol to oxygen, reducing the oxygen to water. The mammalian bloodstream forms of Trypanosoma brucei depend solely on TAO for respiration. The inhibition of TAO by salicylhydroxamic acid (SHAM) or ascofuranone is trypanocidal. TAO is present at a reduced level in the procyclic form of T. brucei, where it is engaged in respiration and is also needed for developmental processes. Alternative oxidases similar to TAO have been found in a wide variety of organisms but not in mammals, thus rendering TAO an important chemotherapeutic target for African trypanosomiasis.

A type II ribonuclease H from Leishmania mitochondria: an enzyme essential for the growth of the parasite

Replication of kDNA in the mitochondrion of the kinetoplastid protozoan is an essential process. One of the proteins that may be required for the kDNA replication is the ribonuclease H (RNase H; EC 3.1.26.4). We have identified four distinct ribonuclease H genes in Leishmania, one type I (LRNase HI) and three type II (LRNase HIIA, LRNase HIIB and LRNase HIIC). We detail here molecular characterization of LRNase HIIC. The coding sequence of LRNase HIIC is 1425 bp in length encoding a 474-amino acid protein with a calculated molecular mass of approximately 53 kDa. While LRNase HIIC shares several conserved domains with mitochondrial RNase H from other organisms, it has three extra patches of amino acid sequences unique to this enzyme. Functional identity of this protein as an RNase H was verified by genetic complementation in RNase H-deficient Escherichia coli. The precursor protein may be enzymatically inactive as it failed to complement the E. coli mutant. The mitochondrial localization signal in LRNase HIIC is within the first 40 amino acid residues at the N-terminus. In vitro import of the protein by the mitochondrial vesicles showed that the precursor protein is processed to a 49-kDa protein. Antisense ablation of LRNase HIIC gene expression is lethal to the parasite cells both in vitro and in vivo. This study not only reveals the significance of the LRNase HIIC in the kinetoplast biology but also identifies a potential molecular target for antileishmanial chemotherapy.

The trypanosome alternative oxidase exists as a monomer in Trypanosoma brucei mitochondria

The bloodstream forms of African trypanosomes solely depend on trypanosome alternative oxidase (TAO), for respiration. Similar to alternative oxidases (AOXs) found in plants and fungi, TAO is a membrane-bound diiron protein. Here, we investigated if TAO exists as a dimer like plant AOXs, or as a monomer like that of fungi. We have found that TAO forms a homo-dimer on a regular SDS-PAGE in the absence of any reducing agent and exists as a monomer under reducing condition. However, TAO does not form a dimer upon treatment of mitochondria with diamide. TAO was found as a higher molecular mass complex on a Blue-native gel after solubilization with digitonin. In the detergent soluble form, TAO activity was stimulated under reducing and inhibited under oxidizing condition. However, these conditions have no effect on the TAO activity in the mitochondria. Moreover, chemical cross-linking analysis revealed that TAO could not be cross-linked when present in the mitochondria. Together, it suggests that like certain other hydrophobic membrane proteins, TAO forms a dimer or oligomer when solubilized with detergents, and the TAO-dimer is SDS-resistant. However, it exists as a monomer in Trypanosoma brucei mitochondria.

The effect of over-expression of the alternative oxidase in the procyclic forms of Trypanosoma brucei

Trypanosome alternative oxidase (TAO) is the cyanide-resistant but SHAM-sensitive terminal oxidase of the mitochondrial electron transport chain in African trypanosomes. The bloodstream forms of Trypanosoma brucei lack cytochromes and respire exclusively via TAO. On the other hand, the insect, or procyclic form possesses a fully developed cytochrome system, and down regulates TAO several folds by reducing the stability of the TAO transcript. We expressed an ectopic copy of TAO in the procyclic form from a tetracycline regulated stable expression vector, in which the TAO 3'-UTR was replaced by T. brucei aldolase 3'-UTR. The TAO transcript produced from the ectopic copy was stably accumulated in the procyclic form. Upon induction with doxycycline, TAO protein level was gradually increased about five-fold within 72 h. TAO over-expression did not show any effect on the growth of the parasite. The rate of respiration and the SHAM-sensitive respiratory pathway capacity was increased about two- and five-fold, respectively, and the cytochrome-mediated respiratory pathway capacity was reduced two- to three-folds within 5 days after induction of TAO. Doxycycline induced TAO+ cells preferentially utilized CN-resistant, SHAM-sensitive pathway of respiration, whereas, in the control cells 70-80% of total respiration was via the CN-sensitive pathway. Moreover, we have found that increased expression of TAO caused about two-fold down regulation of cytochrome oxidase subunit IV, and cytochrome c1 protein level and also caused a four-fold up-regulation of the expression of the surface coat protein, GPEET procyclin in the procyclic form. This suggests that the expression of two terminal oxidases and the coat protein is linked in T. brucei.

Evidence for mitochondrial-derived alternative oxidase in the apicomplexan parasite Cryptosporidium parvum: a potential anti-microbial agent target

The observation that Plasmodium falciparum possesses cyanide insensitive respiration that can be inhibited by salicylhydroxamic acid (SHAM) and propyl gallate is consistent with the presence of an alternative oxidase (AOX). However, the completion and annotation of the P. falciparum genome project did not identify any protein with convincing similarity to the previously described AOXs from plants, fungi or protozoa. We undertook a survey of the available apicomplexan genome projects in an attempt to address this anomaly. Putative AOX sequences were identified and sequenced from both type 1 and 2 strains of Cryptosporidium parvum. The gene encodes a polypeptide of 336 amino acids and has a predicted N-terminal transit sequence similar to that found in proteins targeted to the mitochondria of other species. The potential of AOX as a target for new anti-microbial agents for C. parvum is evident by the ability of SHAM and 8-hydroxyquinoline to inhibit in vitro growth of C. parvum. In spite of the lack of a good candidate for AOX in either the P. falciparum or Toxoplasma gondii genome projects, SHAM and 8-hydroxyquinoline were found to inhibit the growth of these parasites. Phylogenetic analysis suggests that AOX and the related protein immutans are derived from gene transfers from the mitochondrial endosymbiont and the chloroplast endosymbiont, respectively. These data are consistent with the functional localisation studies conducted thus far, which demonstrate mitochondrial localisation for some AOX and chloroplastidic localization for immutans. The presence of a mitochondrial compartment is further supported by the prediction of a mitochondrial targeting sequence at the N-terminus of the protein and MitoTracker staining of a subcellular compartment in trophozoite and meront stages. These results give insight into the evolution of AOX and demonstrate the potential of targeting the alternative pathway of respiration in apicomplexans.

Import and assembly of Neurospora crassa Tom40 into mitochondria of Trypanosoma brucei in vivo

The TOM complex (translocase of the mitochondrial outer membrane) is a dynamic, multisubunit protein complex. Tom40 is the major component of the complex and forms the preprotein conducting pore. To determine if a heterologous Tom40 could be properly targeted and assembled into the Trypanosoma brucei mitochondrial outer membrane, an ectopic copy of a gene encoding Neurospora crassa Tom40 (NcTom40) was expressed in procyclic trypanosomes from a tetracycline regulated procyclic acidic repetitive protein promoter. The level of NcTom40 expression was found to be maximal within 20-26 h of induction with tetracycline. Immunoblot analysis of subcellular fractions showed that NcTom40 was enriched in the mitochondrial fraction. Alkali extraction of isolated mitochondria revealed that NcTom40 was assembled as an integral membrane protein and limited proteolysis demonstrated that it was present in the outer membrane of the mitochondria. These data demonstrate that a heterologous mitochondrial protein containing internal targeting information can be correctly targeted to T. brucei mitochondria. Following blue native gel electrophoresis, the NcTom40 protein was found in a 370 kDa complex which may contain T. brucei Tom components. A 16 kDa protein was coimmunoprecipitated from T. brucei mitochondria containing NcTom40 using antisera developed against the N. crassa protein. The 16 kDa protein may represent a component of the T. brucei TOM complex that associates with NcTom40.

Trypanosome alternative oxidase is regulated post-transcriptionally at the level of RNA stability

In the bloodstream form of African trypanosomes, trypanosome alternative oxidase (TAO), the non-cytochrome ubiquinol:oxidoreductase, is the only terminal oxidase of the mitochondrial electron transport system. TAO is developmentally regulated during mitochondrial biogenesis in this parasite. During in vitro differentiation of Trypanosoma brucei from the bloodstream to the procyclic form, the overall rate of oxygen consumption decreased about 80%. The mode of respiration changed over a 2- to 3-wk period from a cyanide-insensitive, SHAM-sensitive pathway to a predominantly cyanide-sensitive pathway. The TAO protein level gradually decreased to the level present in the procyclic forms during this 3-wk period. However, within the first week of differentiation, the TAO transcript level decreased about 90% and then in the following weeks it reached the level present in the established procyclic form, that is about 20% of that in bloodstream forms. Like other trypanosomatid genes TAO transcript synthesis remains unaltered in fully differentiated bloodstream and procyclic trypanosomes. The half-life of the TAO mRNA was about 3.2 h in the procyclic trypanosomes, whereas the TAO transcript level remained unaltered even after 4 h of incubation with actinomycin D in bloodstream forms. Inhibition of protein synthesis resulted in about a four-fold accumulation of the TAO transcript in the procyclic trypanosomes, comparable to the level present in the bloodstream forms. Thus, TAO is regulated at the level of mRNA stability and de novo protein synthesis is required for the reduction of the TAO mRNA pool in the procyclic form.

Site-directed mutagenesis reveals the essentiality of the conserved residues in the putative diiron active site of the trypanosome alternative oxidase

Trypanosoma brucei possesses a non-cytochrome, salicylhydroxamic acid (SHAM)-sensitive ubiquinol:oxygen oxidoreductase known as trypanosome alternative oxidase (TAO). TAO and similar SHAM-sensitive alternative oxidases (AOXs) contain 2-3 conserved diiron-binding motifs (EXXH). Site-directed mutagenesis of residues H165A, E214A, E266A, and H269L within the conserved EXXH motif abolished the ability of TAO to complement the heme-deficient Escherichia coli strain GE1387. These mutations also reduced the growth of this E. coli auxotroph to about 85% of the control cells containing wild type TAO. In contrast, mutation of residues outside the EXXH motifs, e.g. V205A, L243A, C261A, and V271A, had little effect on complementation, and the reduction in the cell growth was about 5-10%. Mutations of the putative iron-binding residues within the EXXH motifs of TAO abolished the ability to confer SHAM-sensitive respiration to E. coli heme mutant, whereas mutations of the non-conserved/non-iron binding residues resulted in 20-30% reduction of SHAM-sensitive respiration of the E. coli auxotroph. Immunoblot analysis of the total cellular protein of transformed E. coli revealed that the expression level of mutated and wild type TAO (35 kDa) remained unaltered. Mutation at C261A produced a truncated but functional protein of 28 kDa. The addition of ortho-phenanthroline to the growth medium produces a non-functional TAO. The effect of ortho-phenanthroline on the activity of TAO was completely alleviated by the addition of iron in the medium, which suggests that iron is needed for the activity of TAO. This work demonstrates that His-165, Glu-214, Glu-266, and His-269 and the presence of iron are essential for the activity of TAO.

Resection margin status in lumpectomy specimens for duct carcinoma of the breast: correlation with core biopsy and mammographic findings

BACKGROUND

The strategy for surgical treatment of breast carcinoma proven by biopsy is mainly based on the physical and mammographic examinations. To investigate if the pathological findings in core biopsy are contributory to planning the surgical strategy, we correlated the status of ductal carcinoma in situ (DCIS) in the core needle biopsy of breast, the mammographic changes and the status of resection margins in the subsequent lumpectomy.

STUDY DESIGN

Consecutive 130 core needle biopsies with prior mammography and subsequent lumpectomy were reviewed. Biopsies were divided into: group I, DCIS; group II, DCIS and infiltrating carcinoma (IC); and group III, IC. Mammographic findings were categorized into four groups: (a) nonspecific findings; (b) calcification (Ca(++)); Ca(++) and mass, and mass only. The status of margins in correlating lumpectomy specimens was reviewed. Close margin was defined as a free margin at less than 0.1cm from the carcinoma.

RESULTS

The rates of positive or close margins in three groups I, II, and III were 13/18, 18/48, and 2/64 (P < 0.001); and in mammography groups of nonspecific finding, Ca(++), Ca(++) mass and mass only were 5/6, 7/15, 8/37, and 13/72 (P < 0.001), respectively. Of the total of 14 cases with positive margins of more than 0.5 cm in length, 8, 4, and 2 cases were from group I, II, and II, respectively. In addition, 13 of 21 cases with nonspecific changes or with only Ca(++) in mammograms belonged to the group I; 10 of these 13 cases were associated with positive margins. Forty-one of 72 cases presenting as a mass only in mammograms belonged to the group III; only 2 of these 41 cases were associated positive margins.

CONCLUSIONS

Correlation of the extent of carcinoma with pre-operative histopathological findings was better than with mammography. Core biopsies containing only DCIS, particularly in cases with nonspecific findings or with only Ca(++) in mammograms, represent a group of breast carcinoma that pose the high risk for incomplete resection in lumpectomy. Surgical management of patients having these cores includes wider resection margins than would otherwise be taken. Most core biopsies with only IC were associated with negative margins.

Cloning and characterization of a novel serine/threonine protein phosphatase type 5 from Trypanosoma brucei

Reversible protein phosphorylation is essential for the regulation of numerous cellular functions and differentiation. The haemo-flagellated parasitic protozoan Trypanosoma brucei, the causative agent for African trypanosomiasis undergoes various stages of cellular differentiation during its digenetic life cycle. A complete cDNA of a unique serine/threonine phosphatase type five (TbPP5) was cloned and characterized from T. brucei. TbPP5 contains an open reading frame of 1416 bp that encodes a protein of about 53 kDa and exists as a single copy gene in the T. brucei genome. The deduced amino acid sequence showed 45-48% overall identity and 60-65% similarity with protein phosphatase 5's (PP5) from different species. Analysis of the primary sequence revealed that TbPP5 contains three TPR motifs at the N-terminal region (amino acid residues 7-107) while the phosphatase catalytic domain occurs in the C-terminal region (amino acid residues 210-410). A TbPP5 cDNA hybridized with a transcript of 2.5 kb which is present at similar levels in the procyclic and the bloodstream forms. However, the level of expression of the TbPP5 protein (52 kDa) detected by an antibody developed against a recombinant protein produced in E. coli was about 2-fold higher in the procyclic than the bloodstream form. The TbPP5 transcript level gradually decreased in cells grown in the logarithmic phase to the stationary phase in culture. Moreover, 18 h serum starvation of the procyclic forms decreased the level of the specific transcript about 3-fold suggesting that this protein may play a role during the active growth phase of the organism. The recombinant protein showed phosphatase activity which was stimulated about 2.6-fold by arachidonic acid with half-maximal activity at 75 microM. Indirect immuno-fluorescence of permeabilized cells revealed that the protein is localized in the cytosol and the nucleus This is the first report for the identification of a type 5 serine/threonine protein phosphatase in an ancient eukaryote such as T. brucei.

Analysis of in vitro activities of herpes simplex virus type 1 UL42 mutant proteins: correlation with in vivo function

The DNA polymerase (pol) catalytic subunit of herpes simplex virus type 1, encoded by UL30, and its accessory factor, UL42 protein, are both essential for the replication of the virus. Because the stable interaction between UL42 and pol renders the pol fully processive for replicative DNA synthesis, disruption of this interaction represents a potential goal in the development of novel antiviral compounds. To better compare the effects of mutations in UL42 protein on its known in vitro functions, mutations were expressed as glutathione-S-transferase (GST)-fusions and the fusion proteins used in affinity chromatography. In this report, we demonstrate the relationship between the abilities of mutant UL42 fusion proteins to bind pol and to stimulate pol activity in vitro, and the abilities of nonfusion mutant proteins to function in viral replication. The pol stimulation assay using GST fusion proteins was found to be a more accurate and sensitive measure of the ability of the UL42 protein to function in vitro than the pol binding assay using the fusion proteins linked to a solid matrix. We also found an excellent correlation between the ability of purified GST fusion proteins to stimulate pol activity in vitro and the ability of full-length nonfusion UL42 mutant genes to support DNA replication in infected cells. Our results demonstrate that two noncontiguous stretches of amino acids, from 137 to 142 and from 274 to 282, are essential for UL42 function in vivo and in vitro. Although mutant d241-261 exhibited close to wild-type abilities to stimulate pol activity in vitro, it was not capable of complementing the replication of a UL42 null mutant virus. The region of UL42 protein within or close to 241-261 may serve to hinge the essential regions within the N- and C-terminal portions of the protein which are thought to interdigitate. It is hypothesized that reduction in the length of the hinge region could alter the ability of UL42, and/or its complex with pol, to function with one or more of the other proteins present in the DNA replisome within infected cells.

Biochemical and molecular properties of the Trypanosoma brucei alternative oxidase

The protozoal parasite Trypanosoma brucei depends on a mitochondrial non-cytochrome terminal oxidase known as the trypanosome alternative oxidase (TAO) in its mammalian host. We have recently cloned the cDNA from T. brucei bloodstream form and have characterized a 33 kDa mitochondrial protein as TAO. Here we report that the TAO is a single copy gene in T. brucei and its expression is down regulated at the level of transcript abundance during differentiation from the bloodstream to the procyclic trypanosomes. Like other alternative oxidases (AOXs) cloned from different plants and fungi, TAO possesses the conserved sequences at the centrally located predicted membrane spanning domains and the signature sequence at the C-terminal hydrophilic domain for a pair of putative iron binding motifs (E-X-X-H). Phylogenetic analysis of the deduced protein sequences of eight different alternative oxidases cloned from different plants and fungi revealed that TAO is more closely related to the alternative oxidases of the fungi clade than that of plants. TAO has been functionally expressed in Escherichia coli. In the first of the two putative iron binding motifs, site-directed mutagenesis of E215 to A, L, N and Q resulted in the loss of the ability of the TAO gene to complement the heme deficiency of the E. coli mutants (SASX41B and GE1387) by conferring on them a CN-insensitive pathway of respiration. The conservative substitution of E215 by aspartate and histidine reduced the growth of the E. coli auxotrophs by approximately 80%. The mutations apparently did not have any effect on the stability of the expressed protein as revealed by the immunoblot analysis of the bacterial protein using TAO monoclonal antibody, which we have developed. Together, these points suggest that E215 plays an important role in the function of TAO. The steady state level of TAO mRNA is down-regulated in the procyclic stage presumably accounting for the low levels of TAO protein in these forms.

A clinicobacteriological study on leucorrhoea

The pathogens like Trichomonas vaginalis (4.5%), N gonorrhoeae (2.7%) and C albicans (6.7%) were exclusively present in leucorrhoea. The other potential agents with their respective percentages in normal women and cases of leucorrhoea were U urealyticum (21.2% and 50.2%), actinomyces (29.7% and 41.6%), Chlamydia trachomatis (17% and 48.8%), candida-like organisms (CLO) (1.2% and 9.5%) and non-group B streptococci (4.2% and 16.7%). The percentages of urethral syndrome (65.8%), vaginal irritation (63.4%), sore vulva (17%), cervicitis (13.4%), cervical erosion (11%) of the STD clinic were more than those of gynaecological cases. The latter group more often revealed infertility (15.8%) and pelvic inflammatory disease (13.6%). The exclusive isolation rate of N gonorrhoeae (7.3%) and prevalence of G vaginalis (19.5%) and Trichomonas vaginalis (8.5%) in the STD clinic were notable. The cases of gynaecological clinic more commonly showed C albicans (8%) and CLO (13.6%). Significant differences pertaining to U urealyticum (leucorrhoea and inapparent group p < 0.01; leucorrhoea and normal cases p < 0.01), M hominis (leucorrhoea and inapparent group p < 0.05; leucorrhoea and normal cases p < 0.01), Chlamydia trachomatis (leucorrhoea and normal cases p < 0.01) and also actinomyces (leucorrhoea and normal cases p < 0.01; inapparent and normal cases p < 0.05) were recorded. There was conspicuous association of U urealyticum, M hominis, G vaginalis, Chlamydia trachomatis, CLO and actinomyces with leucorrhoea. An almost exclusive presence of Staph aureus, Esch coli and Klebsiella in cases of leucorrhoea appeared meaningful.

Kinetics of theophylline in apnea of prematurity in small for gestational age babies

OBJECTIVES

To study the pharmacokinetics of theophylline and its correlations to pharmacodynamic effects in apnea of prematurity in small for gestational age babies.

DESIGN

Prospective case control study.

SETTING

Level III Neonatal Intensive Care Unit.

SUBJECTS

Ten small for gestational age (SGA) babies and 10 gestation matched appropriate for gestational age (AGA) babies with recurrent apnea of prematurity.

METHODS

All babies were investigated to exclude secondary causes of apnea. 5 mg/kg of aminophylline loading dose followed by 2 mg/kg as maintenance dose every 8 hourly intravenously was used. The trough and peak levels of theophylline were assessed on different days of therapy. Clinical monitoring was done for the efficacy and toxicity of the drug. Analysis was done using unpaired Student's 't' test and the correlation between plasma theophylline levels of different days was performed by using ANOVA.

RESULTS

The therapeutic drug levels were achieved within 24 hours in all babies. The SGA babies showed 25% higher drug levels as compared to AGA babies. The mean trough plasma theophylline levels ranged from 8.15 +/- 1.59 to 12.37 +/- 1.54 micrograms/ml in SGA babies while in AGA babies they ranged from 6.26 +/- 1.93 to 9.96 +/- 1.96 micrograms/ml in first 8 days of therapy. The mean peak levels in SGA babies ranged from 11.91 +/- 1.84 to 17.13 +/- 1.63 micrograms/ml and in AGA babies ranged from 8.17 +/- 1.84 to 13.02 +/- 1.48 micrograms/ml. Twenty per cent SGA and AGA babies each developed clinical toxicity though toxic drug levels were found in 50% SGA and 30% AGA babies.

CONCLUSION

There is a need to modify dosage schedule for these babies.

Reduced renal fractional excretion of lithium in cystic fibrosis

We hypothesized that patients with cystic fibrosis would have abnormal lithium handling because the genetic defect in cystic fibrosis encodes an ion channel which causes a generalized electrolyte transport disorder in epithelial membranes. Eight patients with cystic fibrosis and eight age-sex matched healthy subjects ingested 600 mg lithium carbonate and had urine and serum lithium levels assessed 24 h later. Compared with healthy subjects, the patients with cystic fibrosis had higher serum lithium levels (0.071 +/- 0.038 vs 0.113 +/- 0.055 mmol l-1, P = 0.03) and had lower fractional renal excretion of lithium (27.5 +/- 14.8 vs 18.8 +/- 9.3%, P = 0.03). Caution should be used in prescribing standard doses of lithium to patients with cystic fibrosis until more definitive data are available.

Pathogenic potential of Gardnerella vaginalis on the female urogenital system

The prevalence of certain characteristics of genital discharge like (a) watery variety in sexually transmitted disease (STD) clinic 34% and in gynaecology clinic 26.6%, (b) fishy odour in STD clinic 29.2% and in gynaecology clinic 12.2% and (c) pH > 4.5 in STD clinic 53.6% and in gynaecology clinic 43% was notable. On the other hand, occurrence of "clue cells" (in STD clinic 41.4% and in gynaecology clinic 39.5%) did not show difference in the aforesaid clinics. The preponderance of watery discharge in the STD clinic appears to be related to G vaginalis (in STD clinic 26.8% and in gynaecology clinic 9.3%). It is intriguing to note that G vaginalis was isolated from leucorrhoea (in STD clinic 19.5% and in gynaecology clinic 9.3%) and inapparent (in 10%) cases and normal (in 4.2%) cases. Single infection with G vaginalis in one particular case had profuse watery discharge, pH > 4.5 and there was occurrence of "clue cells". Likewise, in multiple infections revealing G vaginalis (29 cases) as one of the potential agents, 78.5% had profuse, 53.8% watery discharge of which 53.5% had "clue cells" and 81% had pH > 4.5. In mixed type of infections, the U urealyticum (53.8%) and M hominis (30.6%) were conspicuous in bacterial vaginosis. Cervicitis, erosion cervix or urethral syndrome were unrelated to G vaginalis. All cases of G vaginalis infection responded to metronidazole with remission of leucorrhoea in 25.9% cases.

Breast lumps: a study of 10 years

A retrospective study of lumps in the breast sent for histopathological examination in Calcutta National Medical College for a period of last 10 years was done. It was found that 2062 cases (6.82%) of histopathological examination of breast lump were studied out of a total 30208 specimens during that period. There were 1528 cases from benign breast lesions and 504 cases from the malignant breast lesions. The most common lesion found histologically was fibro-adenoma in 950 cases. Others included 150 cases of inflammatory breast diseases of which 36 cases were diagnosed as tuberculosis, 386 cases as fibrocystic disease and 42 cases as other benign neoplastic diseases. Out of 504 malignant cases 456 had carcinoma and 48 had sarcoma. Only 30 cases of male breast lesions were sent of which only a single case of infiltrating duct carcinoma was found, 28 cases had gynaecomastia and one case showed the evidence of fibrocystic disease.

Identification and partial purification of a stage-specific 33 kDa mitochondrial protein as the alternative oxidase of the Trypanosoma brucei brucei bloodstream trypomastigotes

The glycerophosphate oxidase (GPO), the unique terminal oxidase of bloodstream trypanosome (TAO), appears to be functionally similar to the alternative oxidases of some plants and higher fungi. Immunoblotting of mitochondrial proteins of bloodstream trypomastigotes of Trypanosoma brucei with monoclonal or polyclonal antibodies to Sauromatum guttatum (voodoo lily) and Symplocarpus foetidus (skunk cabbage) alternative oxidases respectively revealed two proteins of about 33 kDa (p33) and 68 kDa (p68). These proteins are not present in procyclic trypomastigotes. Electrophoresis under rigorous denaturing conditions indicated p68 to be the dimer of p33. Indirect immunofluorescent studies of bloodstream and procyclic trypomastigotes with monoclonal antibody to plant alternative oxidase also showed the localization of 33 kDa protein in the mitochondria of the bloodstream trypomastigotes. The functional TAO activity could be solubilized efficiently from the mitochondrial membrane of the bloodstream trypomastigotes by 1% NP-40 or 10 mM lauryl maltoside. When fractionated by Superose 12 gel filtration chromatography, p33 was co-purified with the TAO enzymatic activity. The apparent molecular size of the active enzyme complex was found to be 160 kDa. Gradual disappearance of the 33 kDa protein and the TAO enzymatic activity were well correlated during in vitro differentiation of the bloodstream to procyclic trypomastigotes. This study implies that the net biosynthesis of p33, an essential subunit of TAO, is decreased during differentiation from bloodstream to procyclic trypomastigotes.

Functional and behavioral responses as marker of illness, and outcome in infants under 2 months

Value of abnormal findings on 11 functional and behavioral items were studied for identification of serious illness, presence of bacteremia and prediction of the outcome (recovery or death) in infants upto 2 months of age. All the items were graded on a 3 point scale (0, 1 and 2) in the ascending order of severity. A total of 116 infants who were being evaluated for suspected sepsis were enrolled. The assessment was completed before detailed history and physical examination. Significant associations were observed between presence of serious illness and six items by lambda2-test and/or Pearson's correlation and multiple stepwise regression analysis. These were decreased activity, abnormal quality of cry, presence of pallor, fast breathing, decreased consolability, and consciousness level. The sensitivity of six item model was > 90% and negative predictive value >95%. The negative predictive value of several individual items was also above 90%. Consciousness level was the most important predictor of the outcome followed by poor feeding, hydration, color, consolability and abnormal expression (combined multiple R = 0.51). A total score of 7 or more on above six items had a sensitivity of 80%, and negative predictive value of 97% for death. In conclusion, behavior and functional responses (as mentioned above) were fairly useful in predicting the outcome and/or the severity of the illness. These items may be combined to develop a scale to help in therapeutic decision making.

The phosphotyrosine interaction domain of SHC recognizes tyrosine-phosphorylated NPXY motif

Reversible assembly of intracellular signaling complexes is, in some cases, mediated by direct binding of a Src homology 2 (SH2) domain of one protein to a phosphotyrosine moiety of another protein (Cantley, L. C., Auger, K. R., Carpenter, C. L., Duckworth, B., Graziani, A., Kapeller, R., and Soltoff, S. (1991) Cell 64, 281-302). Using a degenerate phosphotyrosine-containing peptide library, we showed that individual SH2 domains recognize phosphotyrosine in a specific sequence context to provide fidelity in signaling (Songyang, Z., Shoelson, S. E., Chaudhuri, M., Gish, G., Pawson, T., Haser, W. G., King, F., Roberts, T., Ratnofsky, S., Lechleider, R. J., Neel, B. G., Birge, R. B., Fajardo, J. E., Chou, M. M., Hanafusa, H., Schaffhausen, B., and Cantley, L. C. (1993) Cell 72, 767-778). Recently a second type of phosphotyrosine interaction domain (PID) or phosphotyrosine-binding domain (PTB) was discovered in the amino terminus of the SHC proto-oncoprotein (Kavanaugh, W. M., and Williams, L. (1994) Science 266, 1862-1865; Blaikie, P., Immanuel, D., Wu, J., Li, N., Yajnik, V., and Margolis, B. (1994) J. Biol. Chem. 269, 32031-32034). Here we demonstrate, using a phosphotyrosine peptide library, that the SHC PID domain preferentially binds to the sequence Asn-Pro-Xaa-phosphotyrosine. This motif is in agreement with sequences at sites implicated in in vivo SHC binding. These results indicate that while SH2 domains predominantly interact with specific residues carboxyl-terminal of phosphotyrosine, the PID domain has high specificity for residues amino-terminal of phosphotyrosine.

Phosphatidylinositol 3-kinase p85 SH2 domain specificity defined by direct phosphopeptide/SH2 domain binding

We have developed a competition binding assay to quantify relative affinities of isolated Src-homology 2 (SH2) domains for phosphopeptide sequences. Eleven synthetic 11-12-amino acid phosphopeptides containing YMXM or YVXM recognition motifs bound to a PI 3-kinase p85 SH2 domain with highest affinities, including sequences surrounding phosphorylated tyrosines of the PDGF, CSF-1/c-Fms, and kit-encoded receptors, IRS-1, and polyoma middle T antigens; matched, unphosphorylated sequences did not bind. A scrambled YMXM phosphopeptide or sequences corresponding to the GAP or PLC-gamma SH2 domain binding motifs of the PDGF, FGF, and EGF receptors bound to the p85 SH2 domain with 30-100-fold reduced affinity, indicating that this affinity range confers specificity. Binding specificity was appropriately reversed with an SH2 domain from PLC-gamma: a phosphopeptide corresponding to the site surrounding PDGF receptor Tyr1021 binds with approximately 40-fold higher affinity than a YMXM-phosphopeptide. We conclude that essential features of specific phosphoprotein/SH2 domain interactions can be reconstituted using truncated versions of both the phosphoprotein (a phosphopeptide) and cognate SH2 domain-containing protein (the SH2 domain). SH2 domain binding specificity results from differences in affinity conferred by the linear sequence surrounding phosphotyrosine.

SH2 domains recognize specific phosphopeptide sequences

A phosphopeptide library was used to determine the sequence specificity of the peptide-binding sites of SH2 domains. One group of SH2 domains (Src, Fyn, Lck, Fgr, Abl, Crk, and Nck) preferred sequences with the general motif pTyr-hydrophilic-hydrophilic-Ile/Pro while another group (SH2 domains of p85, phospholipase C-gamma, and SHPTP2) selected the general motif pTyr-hydrophobic-X-hydrophobic. Individual members of these groups selected unique sequences, except the Src subfamily (Src, Fyn, Lck, and Fgr), which all selected the sequence pTyr-Glu-Glu-Ile. The variability in SH2 domain sequences at likely sites of contact provides a structural basis for the phosphopeptide selectivity of these families. Possible in vivo binding sites of the SH2 domains are discussed.

SH2 domains exhibit high-affinity binding to tyrosine-phosphorylated peptides yet also exhibit rapid dissociation and exchange

src homology 2 (SH2) domains of intracellular signaling molecules such as phospholipase C-gamma and phosphatidylinositol 3'-kinase-associated protein p85 represent recognition motifs for specific phosphotyrosine-containing regions on activated growth factor receptors. The binding of SH2 domains to activated growth factor receptors controls the interaction with signaling molecules and the regulation of their activities. In this report, we describe the kinetic parameters and binding affinities of SH2 domains of p85 toward short phosphotyrosine-containing peptides with the amino acid sequence motif YMXM, derived from a major insulin receptor substrate, IRS-1, by using real time biospecific interaction analysis (BIAcore). Associations were specific and of very high affinity, with dissociation constants of 0.3 to 3 nM, between phosphopeptides and the two separate SH2 domains contained within p85. Nonphosphorylated peptides showed no measurable binding, and the interactions were specific for the primary sequence very close to the phosphotyrosine residue. Moreover, the interactions between phosphopeptides and SH2 domains of other signaling molecules were of much lower affinity. Interestingly, the binding of the SH2 domains to the tyrosine-phosphorylated peptides was of high affinity as a result of a very high on rate, of 3 x 10(7) to 40 x 10(7)/M/s; at the same time, the rate of dissociation, of 0.11 to 0.19/s, was rapid, allowing for rapid exchange of associating proteins with the tyrosine phosphorylation sites.

YMXM motifs of IRS-1 define substrate specificity of the insulin receptor kinase

Of 34 tyrosine residues in insulin receptor substrate 1 (IRS-1), 14 are adjacent to acidic residues, suggesting that they might be phosphorylation sites. Synthetic peptides corresponding to sequences surrounding these tyrosines were used as substrates of the insulin receptor kinase. Surprisingly six of these, each within YMXM motifs, were phosphorylated with greatest efficiency (Km, 24-92 microM; kcat/Km, 0.6-2.1 x 10(4) M-1.sec-1). Substituted YMXM peptides revealed a strong preference of the insulin receptor kinase for methionine at Y + 1 and Y + 3 positions. When phosphorylated, related YMXM sequences are recognition motifs for binding to proteins with src-homology (SH2) domains. The combined hydrophobic and flexible nature of methionine side chains adjacent to the targeted tyrosines provides a versatile contact for recognition by diverse proteins involved in signal transduction.

Structures of the N-linked oligosaccharides of Gp63, the major surface glycoprotein, from Leishmania mexicana amazonensis

The extent of protein N-glycosylation in Leishmania mexicana amazonensis has been proposed to be a factor in the virulence of the parasite. The N-linked oligosaccharides of gp63, the major surface glycoprotein of L. mexicana amazonensis, were characterized after their release by hydrazinolysis, re-N-acetylation, and reduction with NaB3H4. High voltage paper electrophoresis of the reduced oligosaccharides revealed only neutral species. Gel-permeation chromatography on Bio-Gel P-4 yielded four fractions, and the oligosaccharides present were structurally characterized by sequential exoglycosidase digestion, fragmentation by acetolysis, and methylation analysis. Four major structures were found and were biantennary oligomannose type with compositions of Glc1Man6GlcNAc2 (La), Man6GlcNAc2 (Lb), Man5GlcNAc2 (Lc), and Man4GlcNAc2 (Ld). The largest oligosaccharide (La) was shown to contain a terminal glucopyranosyl residue on the alpha (1----3) arm. The biantennary oligomannose structures (Lb and Lc) and the glucosylated structure Glc1Man6GlcNAc2 (La) have not previously been reported as a component of a mature glycoprotein from any source.

Urinary androgen concentrations and social status in two species of free ranging zebra (Equus burchelli and E. grevyi)

In both species of zebra, breeding males had higher urinary androgen concentrations (ng androgens/mg Cr) than did non-breeding bachelor males (30.0 +/- 5.0 (N = 9) versus 11.4 +/- 2.8, (N = 7) in the plains zebra; 19.0 +/- 2.2 (N = 17) versus 10.7 +/- 1.2 (N = 14) in the Grevy's zebra). In the more stable family structure of the plains zebra (single male non-territorial groups) variations in androgen concentrations could not be ascribed to any measured variable. In the Grevy's zebra, androgen values were significantly lower in samples taken from territorial (breeding) males which had temporarily abandoned their territories (N = 4) and the urinary androgen concentration for a male on his territory was negatively correlated with the time since females last visited the territory.

Surface acid proteinase (gp63) of Leishmania mexicana. A metalloenzyme capable of protecting liposome-encapsulated proteins from phagolysosomal degradation by macrophages

Acid proteinase activity is associated with the major surface glycoprotein (gp63) of both extracellular promastigotes and intracellular amastigotes of the parasitic protozoan, Leishmania mexicana. The enzyme purified by monoclonal affinity chromatography from promastigotes is strongly inhibited by metal ion chelators, which is reversible by the addition of Zn(II). This proteinase loses its activity after dialysis against 1,10-phenanthroline. The apoenzyme thus prepared is reactivated substantially by Zn(II) and partially by Cu(II), Cd(II), Co(II), or Ni(II). From the recently published structure of the gene encoding gp63, we identify hitherto unrecognized sequences, which can be aligned to the consensus zinc-binding sites of other known metalloproteinases. Anti-gp63 polyclonal antibodies, but not the monoclonals, precipitate similar molecules from amastigotes. These molecules differ slightly from gp63 in electrophoretic mobility but have similar endopeptidase activity. Phagolysosomal degradation by macrophages of proteins entrapped in liposomes is prevented by coating them with native gp63. This protection is lost with heat denaturation of gp63 to kill its enzymatic activity. The proteolytic activity of the metalloenzyme on the surface of these parasites may thus protect their membrane from cytolytic damages during their survival, differentiation, and multiplication in the phagolysosomes of macrophages.

Factor interactions with the simian virus 40 early pre-mRNA influence branch site selection and alternative splicing

To study the interaction of splicing factors with the simian virus 40 early-region pre-RNA, which can be alternatively spliced to produce large T and small t mRNAs, we used an in vitro RNase protection assay that defines the 5' boundaries of factor-RNA interactions. Protection products reflecting factor interactions with the large T and small t 5' splice sites and with the multiple lariat branch site region were characterized. All protection products were detected very early in the splicing reaction, before the appearance of spliced RNAs. However, protection of the large T 5' splice site was detected well before small t 5' splice site and branch site protection products, which appeared simultaneously. Oligonucleotide-targeted degradation of small nuclear RNAs (snRNAs) revealed that protection of the branch site region, which occurred at multiple sites, required intact U2 snRNA and was enhanced by U1 snRNA, while protection of the large T and small t 5' splice sites required both U1 and U2 snRNAs. Analysis of several pre-RNAs containing mutations in the branch site region suggests that factor interactions involving the multiple copies of the branch site consensus determine the selection of branch points, which is an important factor in the selection of alternative splicing pathways.

Antagonists of luteinizing hormone releasing hormone bind to rat mast cells and induce histamine release

It was reported previously that administration of certain synthetic antagonists of LHRH to rats produced allergy-like symptoms that were attributed to their histamine releasing action. In the present study the interaction of LHRH analogs with rat peritoneal mast cells was investigated in vitro. Potent antagonists of LHRH showed strong in vitro histamine releasing activity from rat peritoneal mast cells. Membrane preparations of rat pituitary glands showed specific binding of radioiodinated LHRH antagonist as well as LHRH agonist. However, rat peritoneal mast cells and membrane preparations from those cells bound antagonist but not the agonist. Furthermore, the LHRH antagonist did not bind to membranes prepared from tissues such as prostate, liver, kidney, and brain. Competitive displacement curves of the [125I]-antagonist with different LHRH analogs showed that the ability of the analogs to compete for binding sites on mast cells was related to their histamine releasing activity. We conclude that histamine release from rat mast cells induced by LHRH analogs is mediated by specific binding of the active peptides to cell membranes. Furthermore, using rat mast cells, the binding assay in conjunction with histamine releasing assay may be utilized to predict the in vivo histamine releasing potential of new LHRH peptides which are of clinical importance.

Urinary steroid concentrations during natural and gonadotrophin-induced oestrus and pregnancy in the giant panda (Ailuropoda melanoleuca)

Urinary concentrations of conjugated oestrone and pregnanediol-3-glucuronide were measured during and after spontaneous and induced oestrus and during pregnancy. Behavioural oestrus was preceded by a rise in oestrone values from less than 10 ng/mg creatinine (Cr) to peaks of 45 ng/mg Cr. Maximal lordotic response and mating activity coincided with the decline in oestrone levels. After presumed ovulation, urinary pregnanediol glucuronide concentrations increased from less than 5 to 15-30 ng/mg Cr. Further increases in this steroid (to 60-80 ng/mg Cr) occurred 114 days after mating, presumably coincident with implantation. These high levels of pregnanediol glucuronide were maintained for 3 weeks, began to decline 1 week before parturition and fell to a nadir (less than 5 ng/mg Cr) immediately after delivery. When FSH was administered i.m. for 5 days, urinary oestrone values rose markedly and were maximal (580 ng/mg Cr) on Day 7. Mating first occurred on Day 20 and 500 i.u. hCG were given i.m. Urinary pregnanediol glucuronide levels during the next 5 months were similar to those in the previous year during pregnancy with values rising 105-108 days after mating. However, no birth occurred. These results support the suggestion that pandas exhibit delayed implantation and demonstrate that the panda is responsive to exogenous gonadotrophins.

Induced type-B reticulum cell neoplasia in mice III. The importance of T-cell proliferation and cellular relocation in accessory cell transformation

After the transfer of spleen cells from old CBA/T6T6 mice (greater than 75 weeks) into young syngeneic CBA/Ca recipients there usually follows a selective expansion of the donor T-cell population and the emergence of type B reticulum cell neoplasms (RCN-B), also of donor origin though probably derived not from the T-cells but from lymphoid dendritic accessory cells. As few as one million injected cells led to significant donor T-cell hyperplasia and tumour induction. Injection of cells from young donors did not have such consequences. Similar tumours were induced by transferring syngeneic cells in both C57BL and DBA/2 mice, although in the latter strain there was no requirement for the injected cells to derive from old donors. It appeared that T-cell proliferation was independent of donor accessory cells or RCN-B induction, since injection of enriched T-cells led to few tumours, although the T-cell chimaerism was indistinguishable from that in recipients of unseparated spleen cells. Development of tumours, however, seemed to be dependent upon stimulated T-cells. Recipients of spleen cells from old T-cell-deprived mice did not develop tumours; conversely, tumours, mostly of donor origin, were induced in recipients of young syngeneic cells when an extrinsic stimulus to T-cell proliferation was provided by continued allostimulation. The apparent selectivity of tumorigenesis for donor cells has led to the proposal that cellular relocation, as a result of transfer, may be an important predisposing factor in malignant transformation in circumstances of T-cell stimulation provided by antigenic challenge or by transfer of T-cells from old donors.

The capability for regulation of insulin secretion by somatostatin in purified pancreatic islet B cells during aging

Pancreatic islet B cells from Sprague-Dawley and Fisher 344 rats aged 3-27 months were separated from A and D cells by centrifugation over a linear percoll density gradient, and incubated in vitro with various concentrations of glucose and somatostatin. Elevation of glucose concentration in the incubation medium from 2.6 to 16.7 mM provokes an insulin secretory response that is independent of rat donor age. Inhibition of the insulin secretory response by somatostatin is independent of rat donor age beyond 12 months. These data indicate that the impaired regulation of insulin secretion during aging observed previously in vivo and in vitro in intact islets may not be intrinsic to the B cells, but instead reflect changes in islet paracrine regulatory mechanisms that relate to the quality and/or quantity of endogenous somatostatin and/or glucagon.

Regulation of insulin secretion by glucose during aging

The purpose of this study was to investigate the sensitivity of insulin secretion to glucose and its possible relationship to changes in islet glucose utilization during aging. Pancreatic islets of Langerhans were isolated from male Sprague-Dawley rats aged 2- to 24-months and perifused in vitro with glucose. Insulin concentration was determined by radioimmunoassay. Glucose utilization was assessed by measuring the rate of conversion of 3H-5-D-glucose to 3H-H20. The sensitivity of isolated, perifused islets to glucose was reduced during aging. Less glucose metabolism, however, may be required to elicit comparable release of insulin by islets from old than from young rats.

Neoplasms arising in CBA mice after transfer of spleen cells from syngeneic old donors

Young (15-week-old) CBA/Ca mice were injected intravenously with spleen cells from individual young (15-week-old) or old (18-24-month-old) CBA/T6T6 mice. Samples of peripheral blood were taken at monthly intervals and cultured with phytohaemagglutinin (PHA) to stimulate T lymphocytes into mitosis. In the recipients of young lymphocytes, the percentage of donor cells dividing in these cultures remained low throughout the experiment, but in the recipients of old spleen cells, after an initial period when the percentage of donor cells declined, there was a marked increase in the percentage of donor cells. The interval between the injection and the increase in the proportion of donor cells was very variable. Ten of the 12 recipients of old lymphocytes developed tumours involving the spleen and mesenteric lymph node. They resembled type B reticulum cell neoplasms as described by Dunn & Deringer (1968), and all but two were transplantable. In addition, one mouse that had no evidence of tumour on histological examination nevertheless gave rise to a transplantable tumour. The five tumours on which chromosomal analysis was carried out proved to be of old donor cell origin. Two out of the five recipients of young cells also eventually developed tumours, but these arose later than the others, had a more granulocytic character, and did not transplant.

Recirculating and sessile B cell populations in normal and CBA/N mice

Chromosomally distinguishable syngeneic mice were parabiosed and the resultant chimerism was followed for 6 weeks in the lymphoid organs, by culturing their cells with polyclonal mitogens, lipopolysaccharide (LPS) for B cells and phytohemagglutinin (PHA) for T cells. As expected of a recirculating population, the T cells equilibrated completely. The B cells in lymph nodes (LN) and Peyer's patches (PP) also equilibrated completely, suggesting that they too are recirculating. B cells in the spleen and blood, however, did not equilibrate over this period. After separation of parabiosed mice, the percentage of partner cells in both the recirculating T and B lymphocyte populations declined steadily, but it continued to rise in the LPS-responsive populations in spleen and peripheral blood suggesting that they were derived from precursor populations which were themselves chimeric. Injection of lymphocytes into CBA/Ca or CBA/N mice showed that LPS-responsive populations in LN and spleen localized differently. These results have been interpreted as demonstrating two major populations of LPS-responsive B lymphocytes in the mouse, one recirculating and the other sessile. The recirculating population appears to be the only LPS-responsive population in LN and PP. In the spleen, however, the recirculating cells constitute about a quarter of the LPS-responsive cells, while the rest are sessile cells. The relationship between these two populations has yet to be clarified. CBA/N mice are deficient in both populations but the sessile one appears to be more severely depleted.

A role for somatostatin in the impaired insulin secretory response to glucose by islets from aging rats

The purpose of this study was to investigate a possible contribution by somatostatin to the impairment in glucose-stimulated secretion of insulin during aging. Pancreatic islets of Langerhans were isolated from male Sprague-Dawley rats aged 2- to 24-months and challenged in vitro with effectors of insulin secretion. Concentrations of insulin, glucagon, and somatostatin were determined by radioimmunoassay. The impairment of glucose-stimulated secretion of insulin which characterizes islets isolated from aged rats may be overcome by treatment of islets with antibodies to somatostatin. Enhanced availability and/or effectiveness of endogenous pancreatic somatostatin during aging may be responsible for the modified pattern of glucose-stimulated secretion of insulin.